Oh boy, here we go. Hayes, atheism does not "purport to have knowledge of the infinite". If you want to know what atheism purports, visit http://infidels.org. Some of my papers on atheism are posted there, and I invite you to read and respond to them.
Atheism does not "replace god with a man". Instead, atheism denies that morality comes from unquestionable precepts found in sacred scrolls, whether written by gods or men. The relevant difference between atheism and theism is that one side settles arguments with "X said so", where X is God. There is no "man" or group of men or any other X whose arbitrary whims can settle a moral question for atheists the way that the whims of God can settle moral questions for theists.
Again, if you want to learn about the philosophy of axiology (i.e. the origin and grounding of values), I give references at http://knowinghumans.net/2007/12/euthyphros-is-my-favorite-dilemma.html.
